统计每个学科最受欢迎的老师前N名

package day02
import java.net.URL
import org.apache.spark.rdd.RDD
import org.apache.spark.{Partitioner, SparkConf, SparkContext}
import scala.collection.mutable
/**
* 统计每个学科最受欢迎的老师前N名
*
*利用TreeSet进行数据优化
*/
object SubjectAndTeacher04 {
def main(args: Array[String]): Unit = {
//定义分区的
val topN=2
//设置本地运行
val conf =new SparkConf().setAppName("SubjectAndTeacher04").setMaster("local[*]")
//初始化对象
val sc =new SparkContext(conf)
//从HDFS上读取数据
val lines = sc.textFile("hdfs://hadoop01:9000/sparkTest")
val subjectAndTeacher = lines.map(line => {
val url = new URL(line)
val subject = url.getHost.substring(0, url.getHost.indexOf("."))
val teacher = url.getPath.substring(1)
((subject, teacher), 1)
})
//收集到所有的学科数据
val subjects: Array[String] = subjectAndTeacher.map(_._1._1).distinct().collect()
//自定义一个分区
val subjectPartition = new SubjectPartition(subjects)
//先进行局部聚合,再进行全局聚合
val reduced: RDD[((String, String), Int)] = subjectAndTeacher.reduceByKey(subjectPartition,_+_)
//将新分区后的数据进行排序处理
reduced.foreachPartition(partition=>{
//自定义一个排序规则
val ts = new mutable.TreeSet[((String,String),Int)]()(new SubjectOrdering())
//分区遍历
partition.foreach(item=>{
ts.add(item)
if(ts.size>topN){
ts.remove(ts.last)
//ts = ts.dropRight(1)
}
})
//第二种方法
//
while (partition.hasNext){
//
ts.add(partition.next())
//
if(ts.size > topN){
//
ts = ts.dropRight(1)
//
}
//
}
println(ts.toList.toBuffer)
})
//输出数据
//释放资源
sc.stop()
}
}
/**
* 自定义排序规则
*/
class SubjectOrdering extends Ordering[((String,String),Int)]{
override def compare(x: ((String, String), Int), y: ((String, String), Int)): Int = {
//((学科,老师),票数)
-(x._2.toInt - y._2.toInt)
}
}
/**
* 自定义一个分区
* @param subjects
*/
class SubjectPartition(subjects :Array[String]) extends Partitioner{
//初始化一个map,map中需要传递两个函数,一个是学科,一个是分区
val rules = new mutable.HashMap[String,Int]()
//定义一个分区
var index =0
for (subject <- subjects){
rules += ((subject,index))
index += 1
}
//定义分区的数量
override def numPartitions: Int = subjects.length
//根据传入的key,返回对应的分区
override def getPartition(key: Any): Int = {
//key是元组对象,里面装的是学科和老师
val tuple = key.asInstanceOf[Tuple2[String,String]]
val subject = tuple._1
rules(subject)
}
}

java版本的

package day02;
import jdk.nashorn.internal.objects.NativeArray;
import org.apache.spark.Partitioner;
import org.apache.spark.SparkConf;
import org.apache.spark.api.java.JavaPairRDD;
import org.apache.spark.api.java.JavaRDD;
import org.apache.spark.api.java.JavaSparkContext;
import org.apache.spark.api.java.function.Function2;
import org.apache.spark.api.java.function.PairFunction;
import org.apache.spark.api.java.function.VoidFunction;
import scala.Tuple2;
import java.net.URL;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.TreeSet;
/**
* 统计每个学科最受欢迎的老师前N名
*
*利用TreeSet进行数据优化
*/
public class SubjectAndTeacherDemo {
public static void main(String[] args) {
//创建本地模式
SparkConf conf = new SparkConf().setAppName("SubjectAndTeacherDemo").setMaster("local[*]");
JavaSparkContext sc = new JavaSparkContext(conf);
//读取数据
JavaRDD<String> lines = sc.textFile("hdfs://hadoop01:9000/sparkTest");
//对数据进行处理
JavaPairRDD<Tuple2<String, String>, Integer> subjectAndTeacher = lines.mapToPair(new PairFunction<String, Tuple2<String, String>, Integer>() {
@Override
public Tuple2<Tuple2<String, String>, Integer> call(String s) throws Exception {
URL url = new URL(s);
String subject = url.getHost().substring(0, url.getHost().indexOf("."));
String teacher = url.getPath().substring(1);
return new Tuple2<>(new Tuple2<String, String>(subject, teacher), 1);
}
});
//收集到所有的分区数据,学科
JavaPairRDD<String, String> subjects = subjectAndTeacher.mapToPair(new PairFunction<Tuple2<Tuple2<String, String>, Integer>, String, String>() {
@Override
public Tuple2<String, String> call(Tuple2<Tuple2<String, String>, Integer> tp) throws Exception {
return tp._1;
}
});
//学科转成数组
Object[] subjectArr = subjects.collectAsMap().keySet().toArray();
//自定义一个分区
MyPartitioner2 partitioner= new MyPartitioner2(subjectArr);
//分区内聚合
JavaPairRDD<Tuple2<String, String>, Integer> reduced = subjectAndTeacher.reduceByKey(new Function2<Integer, Integer, Integer>() {
@Override
public Integer call(Integer integer, Integer integer2) throws Exception {
return integer + integer2;
}
});
//分区内排序
reduced.foreachPartition(new VoidFunction<Iterator<Tuple2<Tuple2<String, String>, Integer>>>() {
@Override
public void call(Iterator<Tuple2<Tuple2<String, String>, Integer>> tuple2Iterator) throws Exception {
TreeSet<Tuple2<Tuple2<String, String>, Integer>> set=
new TreeSet<>(new Comparator<Tuple2<Tuple2<String, String>, Integer>>() {
@Override
public int compare(Tuple2<Tuple2<String, String>, Integer> o1, Tuple2<Tuple2<String, String>, Integer> o2) {
return o2._2-o1._2;
}
});
while(tuple2Iterator.hasNext()){
set.add(tuple2Iterator.next());
if(set.size()>2){
set.remove(set.last());
}
}
Iterator<Tuple2<Tuple2<String, String>, Integer>> iterator = set.iterator();
while(iterator.hasNext()){
System.out.println(iterator.next());
//关闭资源
sc.stop();
}
}
});
}
}
class MyPartitioner2 extends Partitioner{
Object[] subjectArr;
HashMap<String,Integer> map =new HashMap<String,Integer>();
public MyPartitioner2(){}
public MyPartitioner2( Object[] subjectArr){
this.subjectArr=subjectArr;
String subject =null;
int index =0;
for (Object obj :subjectArr){
subject=obj.toString();
map.put(subject,index);
index +=1;
}
}
@Override
public int numPartitions() {
return subjectArr.length;
}
@Override
public int getPartition(Object key) {
Tuple2<String, String> tuple2=(Tuple2<String, String>)key;
String subject= tuple2._1;
return map.get(subject);
}
}

最后

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